5.1.1 GPC Overview

Global program checking (GPC), invoked by the -Xlistx option, does the following:

• Enforces type-checking rules of Fortran more stringently than usual, especially between separately compiled routines

• Enforces some portability restrictions needed to move programs between different machines or operating systems

• Detects legal constructions that nevertheless might be suboptimal or error-prone

• Reveals other potential bugs and obscurities

In particular, global checking reports problems such as:

• Interface problems

  • Conflicts in number and type of dummy and actual arguments

  • Wrong types of function values

  • Possible conflicts due to data type mismatches in common blocks between different subprograms

  Usage problems

  • Function used as a subroutine or subroutine used as a function

  • Declared but unused functions, subroutines, variables, and labels

  • Referenced but not declared functions, subroutines, variables, and labels

  • Usage of unset variables

  • Unreachable statements

  • Implicit type variables

  • Inconsistency of the named common block lengths, names, and layouts